I tried to map my analog input value (0..1023) to the sensors min and max pressure values with the map() function.

I spent hours of testing with external pressure meter to get a solution. but my calculated values differs from the measured values. the difference first is small and get bigger with every millibar the sensor gets. In that hours i tested many code versions. thats why i didn't post any code.

Again, post your code. It seems to me that you could be getting issues due to the order of you (integer) math operations. What is the percentage error that you get and does that increase with higher pressure? Is the other pressure señor a more accurate sensor? How do you know? The sensor you have has a 2 % error, so the absolute error will increase with the higher pressure.

Higher Pressure = higher difference (up to ~15%), while i get the correct atmosphere pressure.The other sensor is an external pressure meter (i have done it with 2 different with same values coming out ;-))

Here is my first code. Like i said: I have tested hours and hours with many different functions and code versions. this was my first aproach:

Are the pressure sensors reading from the same reference point (see the post earlier which talked about relative vs absolute).

Have you tried to print intermediate values of the calc to verify it is what you expect?

It should not matter to the arduino, but have you got a stable 5 v voltage? Arduino will return a value referenced thru its own voltage, but if the sensor expects exactly 5 v you may have an issuers it is not accurate.

Your sensor seems to accept a 12-24 supply voltage and returns a 0-5 V result. This wouldseem to imply that the sensor is generating its own regulated 5V voltage regardless of itspower supply. In other words, it is not relying on a regulated 5V supply being made availableto it, from the arduino.

You should use a voltmeter to check that you are getting a plausible voltage on the signalwire going to the arduino.

You should then check that you are getting a plausible numerical output form the analogRead().